In a food processor, combine all of the ingredients from the unsalted butter, down. Pulse until everything is incorporated, then transfer to the refrigerator to let the butter harden.

Prepare grill to medium-high. Season both sides of the steaks with kosher salt and pepper, and grill to desired doneness. Remove steaks from the grill, and place 2 Tbsp. of the butter over each steak to melt. Serve immediately.

A good tip for making this or other compound butters is to roll the butter into "logs". This makes storage and using the butter easier. To serve, just let it soften a bit, then slice off medallions of butter to use. I prefer to use parchment paper for this because it's easier to shape the butter with. For this to work, the butter has to be somewhat firm but still pliable. If it's too soft it won't work. The technique is as follows:

Using a rubber spatula, scape out all the butter from the food processor onto a rectangular piece of parchment paper, rougly 18" long and maybe 10-12" wide, near one side. Spread the butter out somewhat so that it is parallel to the longer side of the paper. The more you spread it out, the thinner and longer butter log will be. Fold up the edge of the paper, and similar to rolling out sushi with a sushi mat, shape the butter into an even log, and continue to roll up until there is no excess paper. Twist both ends of the rolled up paper until the butter is held snug, then freeze or refrigerate until ready to use.